1. Field of the Invention
The present invention relates to an agent for treating chronic fatigue syndrome, which comprises a polysaccharide having a .beta.-1,3-glucoside bond in the main chain as an effective ingredient.
2. DISCUSSION OF BACKGROUND
Chronic fatigue syndrome is a disorder characterized by new onset of debilitating fatigue or exhaustion lasting longer than 6 months associated with chronic or recurrent low-grade fever, pharyngitis, lymphadenopathy, myalgia, arthralgia, sleep disorders, as well as neuropsychologic complaints such as difficulties in cognition and temperament and confusion. The Centers for Disease Control (hereinafter referred to as CDC) in U.S.A. have published an epidemiological case definition for chronic fatigue syndrome, which uses major and minor clinical and laboratory criteria. Case Definition for the Chronic Fatigue Syndrome
A case of the chronic fatigue syndrome must fulfill major criteria 1 and 2, and the following minor criteria: 6 or more of the 11 symptom criteria and 2 or more of the 3 physical criteria; or 8 or more of the 11 symptom criteria.
MAJOR CRITERIA
1. New onset of persistent or relapsing, debilitating fatigue or easy fatigability in a person who has no previous history of similar symptoms, that does not resolve with bedrest, and that is severe enough to reduce or impair average daily activity level below 50% of the patient's premorbid activity level for a period of at least 6 months.
2. Other clinical conditions that may produce similar symptoms must be excluded by thorough evaluation, based on history, physical examination, and appropriate laboratory findings. These conditions include malignancy; autoimmune disease; localized infection; chronic or subacute bacterial disease, fungal disease, and parasitic disease; disease related to human immunodeficiency virus (HIV) infection; chronic psychiatric disease, either newly diagnosed or by history; chronic inflammatory disease; neuromuscular disease or endocrine disease; drug dependency or abuse; side effects of a chronic medication or other toxic agent; or other known or defined chronic pulmonary, cardiac, gastrointestinal, hepatic, renal, or hematological disease.
Specific laboratory tests or clinical measurements are not required to satisfy the definition of the chronic fatigue syndrome, but the recommended evaluation includes serial weight measurements; serial morning and afternoon temperature measurement; complete blood count and differential; serum electrolytes; glucose; creatinine, blood urea nitrogen; calcium, phosphorus, total bilirubin, alkaline phosphatase, serum aspartate aminotransferase, serum alanine aminotransferase; creatine phosphokinase or aldolase; urinalysis; posteroanteior and lateral chest roentgenograms; detailed personal and family psychiatric history; erythrocyte sedimentation rate; antinuclear antibody; thyroid stimulating hormone level; HIV antibody measurement; and intermediate-strength purified protein derivative (PPD) skin test with controls.
If no such conditions are detected by a reasonable evaluation, this criterion is satisfied.
MINOR CRITERIA
Symptom Criteria
To fulfill a symptom criterion, a symptom must have begun at or after the time of onset of increased fatigability, and must have persisted or recurred over a period of at least 6 months (individual symptoms may or may not have occurred simultaneously). Symptoms include:
1. Mild fever-oral temperature between 37.5.degree. C. and 38.6.degree. C., if measured by the patient-or chills. (Note: oral temperatures of greater than 38.6.degree. C. are less compatible with chronic fatigue syndrome and should prompt studies for other causes of illness). PA1 2. Sore throat. PA1 3. Painful lymph nodes in the anterior or posterior cervical or axillary distribution. PA1 4. Unexplained generalized muscle weakness. PA1 5. Muscle discomfort or myalgia. PA1 6. Prolonged (24 hours or longer) generalized fatigue after levels of exercise that would have been easily tolerated in the patient's premorbid state. PA1 7. Generalized headaches (of a type, severity, or pattern that is different from headaches the patient may have had in the premorbid state). PA1 8. Migratory arthralgia without joint swelling or redness. PA1 9. Neuropsychologic complaints (one or more of the following: photophobia, transient visual scotomata, forgetfulness, excessive irritability, confusion, difficulty thinking, inability to concentrate, depression). PA1 10. Sleep disturbance (hypersomnia or insomnia). PA1 11. Description of the main symptom complex as initially developing over a few hours to a few days (this is not a true symptom, but may be considered as equivalent to the above symptoms in meeting the requirements of the case definition). PA1 1. Low-grade fever-oral temperature between 37.6.degree. C. and 38.6.degree. C., or rectal temperature between 37.8.degree. C. and 38.8.degree. C. PA1 2. Nonexudative pharyngitis. PA1 3. Palpable or tender anterior or posterior cervical or axillary lymph nodes.
Physical Criteria
Physical criteria must be documented by a physician on at least two occasions, at least 1 month apart.
Various criteria other than the above-mentioned criteria have been proposed, but new criteria may be established in compliance with the development of study.
The cause of the cronic fatigue syndrome is not clear as present, and no effective treatment has been established.